This application claims Paris Convention priority of German patent application number 199 60 456.8-25 filed Dec. 15, 1999 the complete disclosure of which hereby incorporated by reference.
The invention concerns a hook strap comprising a transverse arm for abutment on a formwork girder, comprising hook-shaped retainers, disposed at the opposing ends of the transverse arm, for engagement below parts of a waler, and comprising tension elements for fixing the hook strap.
A hook strap of this type is disclosed e.g. in the publication DE 22 60 359 A1.
A hook strap is a means for mounting walers to a formwork girder onto which a formwork panel can be mounted and fixed to the top flange. The assembly of formwork panels includes disposing the formwork girder above the walers and rigidly connecting them by means of the hook straps.
The known hook strap is intended only for connecting walers with a lattice girder. The transverse arm of the known hook strap is guided between lattice struts of a lattice girder and can be disposed only transversely to the lattice girder in the area of a junction of two lattice struts which provides a predetermined grid for aligning the walers with respect to the formwork girders. Disadvantageously, the walers cannot be mounted at any location. The connection of two girders, at least one of which does not comprise a lattice profile, can be realized with the known hook strap only if one girder has a through-opening in the area of the waler.
It is the underlying purpose of the present invention to produce a hook strap which can be mounted at any location of a formwork girder or a waler for connecting the formwork girder with the waler.
The above-mentioned object is achieved by a hook strap having a transverse arm formed by a flat ribbon of small thickness. This embodiment allows many different applications of the hook strap according to the invention. At first, the formwork girder and the waler are aligned transversely to one another. Mounting of the hook strap is achieved in that the ribbon-shaped flat transverse arm is disposed onto an outer side of a girder, preferably onto the upper side facing the formwork panel, i.e. the top flange, and subsequently, the tension members engage on the transverse arm. Gradual setting and adaptation of the hook strap in accordance with the invention is possible via said tension elements.
It is possible to select any position on the outer side of the girder since the flat design of a ribbon as a transverse arm does not limit or impede application of the formwork panel. The flat ribbon can be pressed into or adjusted to the material through application of the tension elements such that the surface produced is largely uniform without projecting steps or edges.
The ribbon may be made of a thin metal sheet (steel or spring steel sheet) which, when tensioning the hook strap in accordance with the invention on the girders, adapts optimally to the surface contour of an top flange like a film. The ribbon fits closely on the top flange under tensile stress and can accommodate all forces which occur during tensioning of the tension elements. The ribbon may also be produced of filaments and in addition to metal, also carbon and/or plastic fibers can be used for producing a ribbon for the hook strap in accordance with the invention.
In one embodiment of the invention, the ribbon is approximately 70 mm wide and has a thickness of less than 1 mm, preferably 0.2 mm. A thin designed ribbon of this thickness allows gradual smooth and discreet transition from the surface of the girder to the waler supported on the girder.
The ribbon of the inventive hook strap does not have to be preformed. Therefore, it can be applied to girders of different widths. Under tension, the ribbon adapts to girders of different widths. Since the ribbon does not penetrate but overlap the girder, it is possible to interconnect the most different girder constructions through the inventive hook strap. The junction points on the lattice girders or openings on the girders can be neglected.
If the tension elements are formed by studs of different lengths with screw heads and a tensioning nut, the hook strap can be easily adapted to different girder heights or bolt heights of girders to be connected and to different walers. The ribbon can be adapted to different girder widths without having to change its length.
It is advantageous thereby that some of the ends of the hook-shaped retainers are remote from the flange of a girder which the other ends partially engage beyond. This allows spreading of the retainers in the tension-free state as well as adaptation to the width of the girder beyond which they are intended to engage. Small angular deflections on the retainers effect a great change of the separation between the free ends of the retainers. The smaller the distance between the supporting point of the retainers and the top flange, the larger the adaptation range of the retainers to the most various girder sizes.
It is possible to provide angle sections to reinforce the edge sections. The ribbon may be formed of a tension-proof material (carbon fibers, metal fibers, plastic fibers, carbon metal or plastic ribbons) having thin walls, almost like a foil. The angle sections can accommodate the forces triggered by the clamping elements and introduce them into the ribbon to stress the ribbon uniformly.
The preferred material for the transverse arm formed as flat thin ribbon is spring steel.
The ribbon ends may be welded to the angle sections and/or contained in the angle sections such that the ribbon surrounds the angle sections once or several times to ensure that the ribbon cannot get detached from the angle sections even when large tensioning forces act on the ribbon.